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Wednesday, November 30, 2011

With yesterday's storm out of the region, the ridge that produced record breaking warmth across the region for the last several days has finally moved out, with colder temperatures returning into the area. With partly cloudy skies, high temperatures reached the upper 40s inland, lower 50s in the immediate NYC area, and the lower to mid 50s in Long Island and southern Connecticut. Although these temperatures are much colder than the 70 degree highs observed just two days ago, today still ended up slightly warmer than the average high temperatures, which are currently near 50 degrees.

With weak troughs moving into the region, temperatures will remain slightly above average through Friday, similar to today's temperatures. A strong high pressure will provide sunny skies for the area on Saturday with slightly below average temperatures, peaking below 50 degrees across most of the area, but yet another ridge will build, bringing yet another potential for 60+ degrees early next week. Although this will certainly not be the last surge of mild temperatures in December, it is likely to be the last 60+ degree warm spell for a while, as a temporarily colder pattern affects the region afterwards.

Tomorrow's Outlook:

Tomorrow will bring temperatures similar to those of today across the area. With mostly sunny skies, high temperatures will reach the upper 40s inland, and the lower 50s across the rest of the area. A NW wind is expected tomorrow.

Friday - Monday: Chilly Start, Warm End; 60+ Degrees Return?

As a very weak low pressure moves through the northern Northeast, bringing light snow showers to central and northern New England, temperatures will slightly rise in the area, reaching the upper 40s to lower 50s inland, and the lower to mid 50s across the rest of the area. Increasing clouds are expected towards Friday afternoon, with partly cloudy skies by the evening hours, although as a trough moves into the area, skies will clear overnight as colder temperatures return, dropping into the mid 20s to lower 30s across most of the area. Saturday will be the coldest day of this time frame, with slightly below average highs possible, reaching the mid to upper 40s inland and the upper 40s to lower 50s across the rest of the area, with sunny skies expected as a strong high pressure moves over the region.

Following the pattern over the last month, the set up for Sunday and Monday becomes easily predictable. The high pressure will move offshore, with SW winds bringing warmer temperatures into the region, and with a low pressure developing in the central US, yet another ridge will build into the eastern US. Although this ridge won't bring temperatures as warm as those of last weekend and the early week, well above average temperatures are expected again. Mostly to partly sunny skies are expected on Sunday with highs reaching the lower to mid 50s across the area, possibly in the upper 50s in parts of the immediate NYC area, and with partly cloudy skies on Monday, high temperatures are likely to reach the upper 50s across the area, with lower 60s likely as well in the immediate NYC area.

Tuesday - Friday: Stormy, Then Colder

The map above shows that a wave of low pressure is expected to develop along the cold front on Monday over the southeastern US, bringing heavy rain. This wave of low pressure will keep dry conditions on Monday, but will slowly move northeast, bringing cloudy skies across the area on Tuesday. There is some uncertainty with the timing, as some models quickly bring the front through on Monday night, others such as the GFS bring the front through on Tuesday night, and the ECM stalls the front over the area with moderate to heavy rain lasting through Thursday, but at this time, I am siding with a slower solution, not as slow as the ECM but not as fast as some of the other models, where the front moves through the area around Wednesday, bringing rain between Tuesday and Wednesday, potentially into Wednesday night in the slower case scenario or early Wednesday morning in the faster case scenario. The timing could still change over the next few days, and if the storm ends up far west enough on Tuesday that the rain does not move over the area, even warmer temperatures may be possible on Tuesday with rain on Wednesday into early Thursday. Stay tuned for more information on the early-mid week storm.

Behind this storm, the models have significantly backed away from the intensity of the cold coming in behind the storm. A few days ago, the GFS, ECM and CMC consistently showed a strong trough dropping into the region. With their latest runs, the ridge over the southeastern US fails to fall apart, and instead a brief cold spell moves through the area before temperatures warm up again towards the weekend. Looking through the longer range, the lack of blocking near Greenland continues as the NAO and AO remain positive, with the PNA turning towards negative, all of these phases unfavorable for cold in the eastern US. The ridge in the SE, known as the Southeast ridge, weakens but fails to fall apart, with most of the cold spells through at least 12/15 expected to focus over the central US, weakening as they move towards the East Coast. As a result, it is now becoming likely that temperatures through 12/15 will likely end up near average, potentially slightly above average. Occasional cold spells are expected in this time frame, potentially bringing snow to parts of the Northeast, but the pattern will remain unfavorable for any sustained cold and snow, with no snow potentials in sight for the NYC area in the near future.

Tuesday, November 29, 2011

After a cutoff low pressure formed over the southeastern US yesterday, bringing an unusual late November snowstorm to southwestern Tennessee and Arkansas, the storm moved northeast towards the area today, bringing an end to the 5-day warm spell, when temperatures surged to record breaking temperatures twice, even ending up over 20 degrees warmer than average yesterday. Today's temperatures were slightly colder yet still well above average, peaking in the mid 60s across the area, ending up slightly lower in some areas such as southern Connecticut.

The cold front is currently moving through the area, as can be seen in the radar image posted to the left. The rain is clearing the area much earlier than forecast; I expected the rain to end by at least 12-2 AM, which was faster than some models keeping the rain through 2 AM, yet the rain has already cleared most places west of NYC as of 11 PM. Temperatures will drop tomorrow into the 50s across the area, staying there through Friday, but despite the drop, temperatures will remain above average. After slightly colder conditions on Saturday, temperatures will warm up again for early next week as rain returns into the forecast again.

Tomorrow's Outlook:

Behind the front, a colder air mass will move into the region, bringing colder yet still above average temperatures. As the cold air mass is approaching the area from the southwest, an unusual direction for a cold air mass to enter the region, SW winds are expected tomorrow along with partly sunny skies. High temperatures will reach the lower 50s inland, lower to mid 50s in the immediate NYC area, and the mid to upper 50s in Long Island and southern Connecticut.

Thursday - Sunday: Chilly, But Slightly Warmer Than Average

The trough moving into the area tomorrow will weaken by Thursday, although 850 mb temperatures will remain chilly, bringing chilly temperatures once again to the area, with highs expected to reach the upper 40s inland and the lower 50s across the rest of the area. By Friday, a very weak low pressure will move through the northern Northeast, with a weak ridge rebuilding into the East. This ridge is much weaker than the previous eastern ridges throughout November, and as a result, temperatures will only slightly warm up, reaching the lower to mid 50s across the area with increasing clouds. After partly to mostly cloudy skies in the evening, cloud cover will clear overnight as temperatures drop into the upper 20s to lower 30s across most of the area except for NYC and parts of Long Island.

The coldest temperatures are expected on Saturday, when highs will be near or even slightly below average. With a weak trough moving into the region again, high temperatures will reach the mid to upper 40s across the area, with a few lower 50s possible in parts of the immediate NYC area. Chilly overnight lows are expected again with temperatures similar to or slightly warmer than those of Friday night. As a stronger ridge begins to build into the East on Sunday, temperatures will warm up again, reaching the lower to mid 50s across the area, with the warmest temperatures ending up in the immediate NYC area where widespread mid 50s are expected.

Next Week: Warmer, Stormy, Then Colder

On Sunday, a low pressure will move into the Great Lakes region, bringing some snow to that region as yet another ridge forms over the eastern US. With the cold front moving towards the area on Monday, mild temperatures are expected to continue, with widespread lower to potentially mid 50s likely again on Monday. With the front moving through the region, however, rain is expected to affect the area on Monday into Tuesday, although the exact timing of the rain is still uncertain. Despite the uncertainty with the timing of the rain, it is likely that a trough drops into the region behind this storm, bringing colder than average temperatures across the area for the first time in a while between Tuesday night through at least Thursday. If the latest modeled set up verifies, high temperatures may end up in the upper 30s to lower 40s range across most of the area, with the potential for widespread lows in the 20s. There is more uncertainty beyond Wednesday due to the time range, but temperatures appear to slightly moderate towards the end of the week while still remaining at least slightly colder than average. Stay tuned for more information on the longer range.

Monday, November 28, 2011

***Note: With the hurricane season coming to an end, the "Tropics" page has now been replaced with a "Winter" page. In this page, snow accumulation maps for days 1-3 will be posted for the region, as well as brief discussions on snowstorms and a highlight of any snow potentials in the medium range.***

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Early in the day, a cold front approached the region, bringing mostly cloudy skies across the area, but the cold front quickly retreated to the west during the afternoon and evening as expected due to a cutoff low pressure forming over the southeastern United States, bringing widespread heavy rainfall to that region with cold temperatures. There is enough cold associated with this storm that snow is even falling and accumulating in parts of southwestern Tennessee and Arkansas.

At the same time that the Southeast is seeing a wintry mix, however, the eastern US ridge persisted over the Mid Atlantic and Northeast. The model guidance from yesterday underestimated temperatures across the region by as much as 4-8 degrees, showing highs only in the lower to mid 60s in the area today. Instead, much warmer temperatures were observed, peaking in the mid 60s inland, upper 60s to lower 70s in the immediate NYC area, and the mid to upper 60s across most of Long Island and southern Connecticut. Today's highs set new record high temperatures for this date, such as 70 degrees in Central Park and 68 degrees in Islip, and Newarks' high of 72 degrees tied the previous record. With average highs near 50 degrees, today's temperatures ended up as high as 20-22 degrees above average.

With the cutoff low in the Southeast starting to move northeast towards the region, tomorrow will be the last of the unusually warm days, with high temperatures again reaching the mid to upper 60s across parts of the area. After a few hours of moderate to heavy rain and thunderstorms on Tuesday night, much colder temperatures will return, but despite the cool down, temperatures will remain above the average through next week.

Tomorrow's Outlook:

As previously mentioned, yesterday's models underestimated the warmth the area saw today, and with the latest model guidance slowly trending warmer for tomorrow, it appears that the models may be too cold for tomorrow as well. With SE winds expected as well as increased cloud cover and scattered showers, temperatures will not be as warm as they were today, but the warmth will persist, with highs reaching the lower to mid 60s inland, mid to upper 60s in the immediate NYC area, and the lower to mid 60s across most of Long Island and southern Connecticut. If the steadier rain holds until the evening as expected, temperatures may get close to 70 degrees again in NE NJ.

The storm in the Southeast will approach the area late tonight, with scattered showers developing after at least 12 PM. A line of heavy rain in the Mid Atlantic is expected to move into places from NYC and further west around 8-10 PM tomorrow night and around 9-11 PM in Long Island/S CT, lasting through about 1-2 AM from NYC and further west, and 3-5 AM in Long Island and southern Connecticut. During this time frame, moderate to locally heavy rain will fall along with potential thunderstorms. By the time that the rain ends, at least 1/4 to 3/4 inch of rain is expected to fall across the area, with the highest amounts to the north and west of NYC.

Wednesday - Friday: Cooling Down

Behind the storms on Tuesday night, temperatures will significantly cool down on Wednesday; in comparison to the last few days, when temperatures were in the 60s and lower 70s across the area, high temperatures on Wednesday will only reach the upper 40s to lower 50s inland, lower to mid 50s in the immediate NYC area, and the mid to upper 50s in Long Island and southern Connecticut. Although these temperatures will feel colder compared to the current warmth, these temperatures are still several degrees warmer than average.

With only a weak cold air mass quickly retreating north on Thursday, high temperatures will only drop to about near average during this time frame before warming up again. Thursday will bring mostly sunny skies with slightly colder temperatures, peaking in the upper 40s inland and the lower to mid 50s across the rest of the area, but as a weak disturbance approaches the Northeast, Friday will bring increasing clouds with highs reaching the lower to mid 50s across the area. Cloud cover is expected to decrease later on Friday night as another high pressure approaches, with cold overnight lows dropping into the upper 20s to mid 30s across most of the area.

Next Weekend - Early Next Week: Still Warmer Than Average

Colder temperatures are expected to return on Saturday as the area of high pressure moves in, with high temperatures in the mid to upper 40s across the area, potentially in the lower 50s in parts of the immediate NYC area. Although these temperatures will feel much colder compared to what the area has observed recently, these temperatures are just about near the average for this time of the year, if not 1-2 degrees slightly below the average. Saturday will bring the coldest temperatures of this time frame as yet another ridge builds into the eastern US with a relatively weak low pressure affecting the Great Lakes region. Unlike the warm spells of this month, however, the ridge building in for next weekend into early next week will not be as strong as the current ridge and the previous ones throughout the month.

With 850mb temperatures warming up to about 6-8 degrees celsius, temperatures will begin to slightly warm up on Sunday, reaching the lower to mid 50s across the area. If the currently expected scenario with a low pressure near the Great Lakes on Monday verifies, Monday would bring the warmest temperatures, reaching the mid 50s across most of the area with a few upper 50s possible in the immediate NYC area. In the other scenario, which is less likely but is a possibility, the storm would be weaker with the front already over the region on Monday, which would bring a risk of showers and colder temperatures. With the low pressure near the Great Lakes bringing a cold front towards the region, there is a risk of showers between Monday night and Tuesday night.

Longer Range Overview: Behind the cold front, there is decent agreement from the models showing a strong trough dropping into the north central and then the northeastern US. Although some of the models may be overdoing the intensity and duration of this cold spell, colder temperatures are likely for the second half of next week. With some changes in the Pacific pattern, including a -EPO and +PNA developing which are more favorable for eastern US cold, a colder pattern is expected to set up between December 5 and 15, with more frequent cold temperatures and weaker/less frequent warm spells bringing the potential for slightly below average temperatures in this time frame. As I will discuss in my winter outlook in more details, however, this colder start to December is not a pattern change that will last through the rest of the month, and a warmer pattern may return towards the middle of December once again.

Sunday, November 27, 2011

Note: The 5-Day Forecast will be updated later tonight for the area. In addition, the final winter outlook will likely be posted within the next few days.

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After a more zonal flow developed in the US late last week, a strong ridge built into the eastern half of the US, providing the NYC area with well above average temperatures. On Friday, 11/25, mostly sunny skies were observed with highs reaching the lower to mid 60s from NYC and further west and the upper 50s to lower 60s in Long Island/S CT. The peak high of 64 degrees was observed in Teterboro and Sussex in NJ. Saturday, 11/26, brought the warmest temperatures, surging into the lower to mid 60s inland, in Long Island, and southern Connecticut, with mid to upper 60s in the immediate NYC area. Temperatures as high as 67 and 68 degrees were observed in Teterboro and Newark, respectively. These temperatures matched records in parts of the area, such as Newark. With average high temperatures near 50 degrees, these temperatures were nearly 15-20 degrees above average in parts of the area.

With the ridge still stuck over the region, well above average temperatures will continue through Tuesday, when highs will likely reach the mid to upper 60s again in the immediate NYC area. A cutoff low forming in the southeastern US drifting north will bring a line of moderate to locally heavy rain for the area on Tuesday night. Although no sustained cold will form over the region, this storm will end the consistent warm spells over 60+ degrees as a somewhat colder start to December begins, with near to slightly below average temperatures expected.

Today and Monday:

Temperatures are currently peaking in the upper 50s to lower 60s inland, lower 60s in the immediate NYC area, and the upper 50s in Long Island and southern Connecticut. As a slow moving cold front approaches the area, mostly cloudy skies will continue through the overnight hours as well as some fog, with lows steady in the upper 40s to lower 50s inland and the lower to mid 50s across the rest of the area. To put the positive temperature departures into perspective, tonight's low temperatures will be approximately near the average high temperatures.

With the slow moving cold front approaching the area, tomorrow will bring mostly cloudy skies with fog possible in the morning. Temperatures will remain well above average again, peaking in the lower to mid 60s from NYC and further west and the lower 60s across most of Long Island and southern CT. Although the front will be over the region, it will fail to produce any significant rain until Tuesday night, as I will discuss in more details below.

Monday Night - Wednesday Morning: Storm Ends Record Breaking Warmth

Looking at the current set up over the US, there is a narrow but long trough in the central US, associated with a cold front currently affecting the Ohio Valley and the Southeast, with a strong ridge in the western and eastern US. The southern part of the trough will separate from the main flow and turn into a cutoff low over the southeastern US tomorrow, which will lead to some interesting results over the next few days. With the cutoff low pressure trapping cold air over the southeastern US, places such as northern Mississippi and Memphis, TN will see snow mixing with the rain tomorrow night, while New York City sees dry conditions with temperatures still well into the 60s. Although the cold front will be near the area on Monday, with the southern cutoff low intensifying, the front will retreat to the west on Monday night, with the warmth still persisting through Tuesday.

By Tuesday, the cutoff low will begin to drift north towards the Ohio Valley, bringing a cold front towards the region. With the area still in the warmer part of the system, temperaturess will once again reach the upper 50s to lower 60s across the area, but this time with an east/ESE wind. A line of moderate to locally heavy rain will move through the Mid Atlantic on Tuesday, reaching the area by at least 8-10 PM Tuesday night. As the low pressure merges back into the main flow, colder air from Canada will enter the storm, bringing more snow into places such as Michigan while the colder air mass associated with the cutoff low will move into the area from the south, ending the rain by at least 2 AM Wednesday, with 1/2 to 3/4 inch of rain expected across most of the area but with locally lower amounts still expected, ending up between 1/4 and 1/2 inch in some places. Stay tuned for more information on this storm and its impact on the region.

Wednesday - Friday: Colder, But Still Warmer Than Average
Behind Tuesday night's cold front, Wednesday will bring dry conditions with mostly cloudy skies. Temperatures will cool down significantly but will remain slightly above average, peaking in the upper 40s to lower 50s inland and the lower to mid 50s across the rest of the area. Overnight temperatures will be colder as well, dropping into the lower to mid 30s inland, mid to upper 30s in NE NJ, SE NY except for Orange county, and southern Connecticut, and upper 30s to lower 40s in Long Island and NYC.

With a high pressure moving in, mostly sunny skies are expected for Thursday, but with the cold air mass weakening, slightly above average temperatures will continue, peaking in the upper 40s inland and the lower 50s across the rest of the area. Although colder temperatures are expected for Thursday night, temperatures on Friday will be similar to those of Thursday with mostly to partly sunny skies expected.

Next Weekend And Beyond: Becoming Colder, But Not Very Cold

The pattern throughout November was a warm one, associated with 1-2 day troughs followed by a strong ridge setting up in the eastern US for several days, bringing high temperatures into the 60s. Today ended up as New York City's 11th day this month above 60 degrees; even though November 2009 and 2010 were warm as well, both of these months only had 6 days above 60 degrees in NYC. The warmth was able to settle into the East with the help of the Pacific pattern consisting of a -PNA and +EPO, driving warmth into the United States. The pattern is currently in the process of changing, but even though the change is towards less warmth, the pattern for the first half of December is not one that supports any strong cold and snowstorms.

The EPO is expected to become negative by early December along with a neutral to slightly positive PNA, supporting more ridging near the western US and Alaska. If combined with a -NAO and -AO, the -EPO/+PNA combination can be supportive of cold and snow in the eastern US. In this case, however, the Atlantic pattern is not as suppotive, with the AO remaining positive as well as the NAO, with no blocking west of Greenland to keep the cold locked in place. Although the overall pattern does appear to be a colder one, with weaker and less frequent warmth in between the cold spells, the lack of a -NAO/-AO will keep the cold relatively transient. The potential is there for slightly below average temperatures between December 5 and 15, with more frequent cold spells along with some warmth, and the possibility may be there for at least one snowstorm to affect parts of the region, perhaps including the area should the timing and location end up supportive, during this time frame. Stay tuned for more information about the long range with tomorrow's update, as well as the final winter outlook which will likely be posted within the next few days.

Saturday, November 26, 2011

Due to issues with the computer, no update was posted tonight. An update will be posted on Sunday afternoon discussing the latest outlook, focusing on the mild temperatures lasting through Tuesday, a moderate rain event on Tuesday night/Wednesday, and the seasonable but not very cold temperatures that will follow for the second half of the week.

Thursday, November 24, 2011

With yesterday's storm out of the region, a weak trough moved into the region last night, and has been pushed out today by a strong ridge building in the central US. Temperatures ended up slightly above average as a result, peaking in the lower to mid 50s from NYC and further west, and the upper 40s to lower 50s in Long Island and southern Connecticut. With the ridge in place through Sunday, sunny to mostly sunny skies will continue with warming temperatures, reaching the 65 degree mark in NYC on Saturday, but the warmth will not persist beyond the weekend as a cold front approaches the region, bringing rain again for the first half of next week.

Friday - Sunday: Warming Up

Tomorrow will bring sunny skies for the area with the high pressure over the region, with light WSW winds expected. High temperatures will be warmer than those of today with the large central US ridge spreading east, bringing high temperatures into the upper 50s to lower 60s from NYC and further west and the mid to upper 50s in Long Island/S CT, which is nearly 10-15 degrees above the average high temperature for this time of the year. Saturday will bring mostly sunny skies with even warmer temperatures, reaching the upper 50s to lower 60s in Long Island/S CT and the lower to mid 60s from NYC and further west. The warmest temperatures are expected near NE NJ, where temperatures are expected to reach the 65 degree mark. With a cold front approaching on Sunday, mostly cloudy turning to cloudy skies are expected, with high temperatures in the upper 50s to lower 60s across the area.

Next Week: Uncertainty With Storm

The latest model guidance continues to have a hard time handling the storm for next week, and solutions are now even more different than they were yesterday; the GFS model brings the front through on Sunday night/Monday, the ECMWF pushes the main rain event until Thursday, the UKMET develops a cutoff low over the Great Lakes region, and the CMC brings a strong low pressure on Tuesday into Wednesday, although the CMC solution is most likely an outlier one. The cold front is expected to approach the region by Sunday night into Monday, bringing rain, but what happens afterwards regarding any development of a cutoff low, where that happens, and where is still uncertain. At this time, I am thinking that the system doesn't stall for too long and remains more progressive, with rain likely between Sunday night and Tuesday night, although the exact timing is still uncertain, and it is possible that the rain ends by Monday night or it could last through Wednesday night. Stay tuned for more information on the storm next week.

Wednesday, November 23, 2011

After last night's heavy rain event, today brought mostly drier conditions with occasional showers lasting through the early afternoon hours. Rain totals ended up between 1.5 to 2.25 inches across most of the area, with the highest amounts focusing over NYC, southern Connecticut, and southeastern NY. High temperatures peaked in the morning hours in the mid 40s inland, lower to mid 50s in the immediate NYC area and southern CT, and the upper 50s to lower 60s in Long Island and southern Connecticut, before dropping into the 40s across the rest of the area by the afternoon hours.

With the storm moving out, a brief trough will move into the region tonight into tomorrow, bringing temperatures into the mid 20s to mid 30s across the area tonight, with temperatures on Thanksgiving day reaching the lower to mid 50s with mostly sunny skies expected. A larger ridge will build in for the weekend with well above average temperatures, peaking in the mid 60s near NYC, but a larger storm will approach the region by Sunday and Monday, bringing yet another moderate to heavy rain potential for early next week.

Thanksgiving Weekend Outlook:

With a weak and short lasting trough moving in, seasonable temperatures are expected for tomorrow, peaking in the lower to mid 50s across the area with mostly sunny skies and west winds. A stronger high pressure moving into the region along with a strong, widespread ridge will result in high temperatures peaking in the mid to upper 50s across the area on Friday with sunny skies, and parts of NE NJ and NYC may reach the lower 60s.

The warmest day will be on Saturday, when mostly sunny skies are expected along with high temperatures reaching the lower to mid 60s across the area. The warmest temperatures will be near NE NJ, where temperatures may reach or even slightly pass the 65 degree mark. With a low pressure slowly approaching the region, Sunday will bring mostly cloudy skies with high temperatures slightly cooler than those of Saturday, in the upper 50s to lower 60s across the area, getting close to 65 degrees in parts of the immediate NYC area.

Next Week: Stormy Start, Then Colder

A cold front will slowly approach the region on Sunday and Monday, bringing thunderstorms to parts of the central and southern US. As this front approaches the region, some models develop a cutoff low near the Southeast US, while others such as the GFS stall the front near the region, producing heavy rain for Monday and Tuesday. While there is still some uncertainty with the exact timing, the potential is there for heavy rain to fall during this time frame. At this time, I am thinking that the majority of the rain focuses on Monday into Tuesday, but the timing could end up anywhere from Sunday night to Wednesday due to the large model spread. Tomorrow's update will discuss the outlook for this storm in more details.

Behind this storm, uncertainty with the timing and location of the low pressure by Wednesday are leading to more uncertainty with how the storm merges back into the main flow, but it does appear likely that a stronger cold air mass may drop into the region by the second half of next week. Although with the pattern failing to flip towards conditions supportive of sustained cold, any cold in this time frame will not last for more than a few days at once, colder temperatures are expected for the end of next week, and may potentially end up below average for parts of the region. Stay tuned for more information on the longer range.

Tuesday, November 22, 2011

As a relatively weak yet very moist low pressure developed in the southern US and moved towards the Ohio Valley, today brought cloudy skies across the area with occasional showers. The storm's heavier rains spread into the area this afternoon, and places from NYC and further west are currently observing moderate to locally heavy rain. With the cloud cover and rain, today brought colder temperatures across the area, which ended up colder than expected in NW NJ and interior SE NY, where highs only peaked in the mid to upper 30s, although precipitation type was rain due to above freezing temperatures aloft. Temperatures in the immediate NYC area ranged from the lower to mid 40s in the northernmost suburbs to the upper 40s to lower 50s in NYC, and Long Island/S CT saw temperatures in the upper 40s to lower 50s as well.

The low pressure will continue to move east, bringing as much as 2 to 3 inches of rain in parts of the area, which will result in some flooding as well as placing 2011 as the second wettest year on record for NYC. A strong ridge and high pressure will bring in sunshine just in time for Thanksgiving, and although chilly temperatures are still expected, temperatures will warm up by the weekend, with temperatures passing the 60 degree mark once again. Although this will not be a brief warm spell, the warmth is expected to end around Tuesday of next week as another storm approaches, bringing another risk of heavy rain to the region.

Tonight and Tomorrow: Heavy Rain

Storm Set-Up: The low pressure is currently located near central Ohio. The storm has been moving to the northwest throughout the day, but as it approaches a high pressure to its north, the low pressure will take more of an eastern track, taking it through central Pennsylvania and central New Jersey tonight and tomorrow. The storm originated in the southern US, pushing the warmth along with it further north, and as the storm moves into the Northeast US, it will run into the cold air, producing an axis of heavy snow from the Adirondacks in northern New York to southern/central Maine. The high pressure to the north will keep the cold air stuck in place, resulting in cold temperatures throughout the storm as far south as Sussex county in NJ and Orange county in NY, where temperatures will stay in the upper 30s to lower 40s until tomorrow morning before slightly rising. There is no strong cold air mass associated with this storm, however, and the storm will only pull in a weak and very short lasting trough into the region as it moves out before a more significant ridge builds in, which will be discussed in more details in the next section.

Scenario Forecast: This storm is associated with a lot of moisture, as can be seen with the latest radar posted above showing widespread moderate rain covering the region. As the overnight hours continue, the steady moderate to heavy rain, mixing with snow in northern New England, will spread further northeast, while the NYC area will be in the southern edge of the heavier rain. With more instability further south under the warm sector from eastern Virginia into central NJ, some thunder is possible overnight near NYC, but is not expected north of NYC. To the left, I posted a graphic representing the potential future radar towards 2 AM, when the low pressure will be near the PA/OH border, showing the heavy rain from NYC into central New England, thunderstorms in the southern Mid Atlantic, and developing heavy snow in New England. This map does not account for areas of sleet and freezing rain that will fall between the rain and snow zones in central New England and near central NY.

The heavy rain is expected to continue through about 8 AM on Wednesday morning, when the intensity of the rain will weaken. Occasional showers will continue through the afternoon hours, with cloudy skies and an isolated shower possible for the evening hours. Temperatures overnight will rise across the entire area, peaking in the morning hours in the mid to upper 40s inland, lower to mid 50s in the rest of SE NY excluding Orange county, mid 50s to lower 60s in NE NJ and NYC, lower to mid 50s in southern CT, and upper 50s in Long Island. As the low pressure slides just to the south of NYC during the early afternoon hours, temperatures will drop into the mid 40s to lower 50s across the area by the afternoon hours.

Total Rain Forecast: By the time that the storm ends, at least 1.5 to 2.5 inches of rain are expected in Long Island/S CT with the highest amounts towards southern CT, and between 2 and 3 inches of rain from NYC and further west. These amounts will be capable of producing flooding in some areas, especially west of NYC. In addition, with at least 2-3 inches of rain expected in NYC, this storm will make 2011 the second wettest year on record for Central Park, with nearly 70 inches of rain since January. The wettest year on record was in 1983 with 80.56"; although 10 inches of precipitation are not expected to fall in December to surpass this record, especially if a wet pattern sets up for December, this year could get very close to the record.

Thanksgiving Weekend: Sunny, Dry, Warmer

With the low pressure moving out of the region, skies will clear just in time for Thanksgiving. A high pressure will move into the region on Thursday, at the same time that a weak and very short lasting trough moves into the region. This will result in mostly sunny skies and chilly temperatures, peaking in the upper 40s to lower 50s inland and the lower to mid 50s across the rest of the area. Cold temperatures are expected for Thursday morning, dropping into the mid 20s to lower 30s across northern NJ, SE NY and southern CT, lower to mid 30s in Long Island, and mid 30s in NYC.

With the high pressure slowly moving through the region, a much stronger ridge will build into the eastern half of the US, providing the region with southwest winds and warming temperatures. As a result, sunny skies will continue through Friday and mostly sunny skies on Saturday with warming temperatures, reaching the upper 50s from NYC and further west and the mid to upper 50s east of NYC on Friday. Well above average temperatures are expected for Saturday, reaching the upper 50s to lower 60s across most of the area, and temperatures may get near the 65 degree mark in parts of NE NJ.

Sunday will bring mostly cloudy skies as a low pressure system approaches from the west, with similar high temperatures, in the upper 50s to lower 60s across the area. Although no rain is expected across the area on Sunday, this low pressure will begin what may be a crazier week of weather across the eastern half of the US.

Next Week: Stormy Beginning, Cold End?

The graphic above showing the warm spell for the weekend shows that a low pressure will be moving through Wisconson with its cold front moving east as well. As this system approaches the eastern US, the trough will become neutrally and then negatively tilted as it begins to cut off from the main flow. Exactly where this storm cuts off is still uncertain and will result in timing uncertainty for the rain next week, but at this time, it is likely that the upper level low cuts off over the southeastern US, which would keep mild temperatures in place across the area through Monday while the Southeast sees a cold rain, potentially falling as snow in the higher elevations. The cutoff low is not expected to stick for a long period of time in the Southeast, and once it starts to drift north back towards the main flow, moderate to heavy rain will move into the region. The timing could range any time from Monday afternoon to Wednesday afternoon, but at this time, I am going along with the model consensus supporting Monday night through Tuesday for the rain to affect the region. There is still uncertainty with the timing, but the scenario does support the potential for heavy rain to affect parts of the region regardless of the timing. Stay tuned for more information on the outlook for early-mid next week.

For the longer range, after this storm, some models such as the long range GFS attempt to set up a significantly colder pattern, with no ridge in the southeast. Looking at the overall pattern, there are some changes that will allow more cold air into the central and eastern US for the very end of November into the first week of December, including transient ridging near the Davis Strait west of Greenland, the consistently positive EPO dropping towards neutral, hints of ridging near the west coast, and the displacement of the strong polar vortex near Alaska. These factors will likely play a role in a somewhat colder start to December, but none of these changes appear to be permanent yet as the Pacific pattern, unfavorable for sustained cold, fails to flip to a pattern favorable for East cold, with no sustained west based -NAO block setting up. With the factors above considered, as well as the MJO which continues to move through unfavorable phases for cold in the East, a somewhat colder start to December is expected across the region with average or slightly below average instead of above average temperatures possible, including the second half of next week, although it is likely that the mostly mild pattern with the occasional transient cold spells continues beyond early December through the middle of the month, potentially even longer than that. Even though the more sustained cold and snow will eventually get to the East, it's going to take time for such a pattern to unfold, and it may not be until late December or even January that any sustained winter conditions affect the East, although transient periods of cold and some snow will take place until then. A more detailed write up on the longer range will be included with the winter outlook, which will be posted by the end of the month.

Monday, November 21, 2011

I was unable to work on a detailed discussion for today. Tonight's update reviews the highlights of the forecast for the upcoming week, with some hints on the longer range, and either on Tuesday or on Wednesday (likely on Tuesday) I will have a detailed write-up on the forecast, including a pattern outlook through early December. The winter outlook will be posted by the end of this month.

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Tuesday - Wednesday: A strong low pressure will affect the region during this time frame, with widespread impacts ranging from heavy snow in New England to a severe weather outbreak in parts of the Mid Atlantic. This low pressure will first move towards Ohio, and will then move east through central Pennsylvania before moving towards NYC and then offshore. Occasional showers are expected during the day on Tuesday with highs in the upper 40s to lower 50s across most of the area, but as the storm approaches, rain will become steadier by Tuesday evening, with a soaking heavy rain from about 8-10 PM Tuesday night through 8 AM Wednesday. During this 12 hour period, anywhere from 1.5 to 2.5 inches of rain are expected to fall across the area, likely focusing near 2 inches. Rain Warnings and Heavy Rain Watches will be issued tomorrow afternoon for the area.

Some models have been showing the potential for temperatures to surge above 60 degrees for Wednesday morning with a risk of thunderstorms in the area. While as of yesterday evening, this solution had some support, the latest trend has been to take the storm further south, with the low pressure now modeled to end up near or south of NYC. Although some rumbles of thunder may be possible near or south of NYC, any severe weather risk will stay confined to the Mid Atlantic south of Philadelphia, where I expect to see more widespread thunderstorms along with a 15% risk of severe weather. Otherwise, temperatures will peak in the lower to mid 50s inland and in the mid to upper 50s across the rest of the area with lower 60s south of NYC. The heavy rain is expected to end by 8 AM, with the steady rain ending by at least 12 PM. Cloudy skies will continue for the rest of the day with scattered showers possible through midnight, especially focusing on the evening hours.

Thanksgiving Weekend: A much stronger ridge will build into the region, providing warming temperatures and sunshine for the long weekend. Thanksgiving day will be chilly and breezy along with mostly sunny skies, with highs peaking in the upper 40s to lower 50s across the area. Thursday night will bring mostly clear skies with lows in the lower to upper 30s across most of the area except for NYC, which should see lows in the lower 40s.

With a high pressure overhead, sunny skies are expected for Friday and Saturday with warming temperatures, reaching the mid to upper 50s across the area on Friday and the upper 50s to lower 60s on Saturday. As a cold front slowly approaches the region, increasing clouds are expected on Sunday but with dry conditions lasting along with similar temperatures compared to those of Saturday.

Next Week: There is a decent model consensus for a negatively tilted cold front to move towards the region with a wave of low pressure cutting off, forming an upper level low somewhat similar to the one we saw during late September. The negatively tilted front will move east and will likely affect the area between Monday afternoon and Tuesday. The potential may be there for heavy rain and gusty winds to affect parts of the region, including the area, and if some models verify for this time frame, thunderstorms may be possible as well. This front would then likely be followed by colder temperatures for the middle of next week, and if the right variables fall in place, a somewhat colder but not persistently cold period of time may be possible during the very end of November into early December, although the pattern will not change just yet. The update either tomorrow or on Wednesday will discuss the longer range in more details.

Friday, November 18, 2011

Due to a very busy schedule, I will unfortunately not be able to update the blog this weekend. The next update will be posted on Monday, 11/21. The winter outlook has been delayed as well, and should be posted towards the end of the month.

Thursday, November 17, 2011

- With clearing skies, colder temperatures will return tonight, dropping into the mid 20s to lower 30s across the area with a few mid 30s possible in the warmer parts of NYC.

- As a high pressure builds in, mostly sunny skies are expected tomorrow with below average temperatures. High temperatures will peak in the lower to mid 40s inland and the mid 40s across the rest of the area. A few upper 40s are possible near or SW of NYC.

- With the high pressure sliding offshore, yet another ridge will build across the eastern US, although this ridge won't last as long as previous ones have this month. Temperatures will warm into the lower to mid 50s across the area on Saturday with mostly sunny skies, and on Sunday, as a cold front approaches, partly cloudy skies are expected with highs in the upper 50s to lower 60s across the area. A few mid 60s are possible near or SW of NYC.

- The cold front will be a dry one, bringing mostly cloudy skies for Sunday night and partly cloudy skies for Monday. Temperatures will cool down on Monday into the lower to upper 50s across the area, and again on Tuesday into the upper 40s to lower 50s across most of the area.

- Although there is more uncertainty for the Tuesday-Thursday time frame, it is likely that a storm will affect parts of the region including the NYC area, around Wednesday. With a progressive pattern and a lack of significant phasing, it is unlikely that any storm in this time frame goes too far north of NYC, and a storm track near or south of NYC is favored at this time, likely bringing rain to the area, but with a trough in place during this time frame, the potential may be there for snow to fall in parts of the Northeast and New England if the location and the timing of the storm are supportive. More information will be posted on this potential storm with tomorrow night's update.

Thanksgiving Outlook: With a high pressure returning, mostly to partly sunny skies are likely to return by Thursday. Although the exact temperatures for Thursday depend on Wednesday's storm, chilly temperatures are likely to continue through Thursday, possibly in the upper 40s to lower 50s, but may end up slightly colder or warmer. For the rest of the weekend, with the high pressure over the region, mostly sunny skies are likely to continue with temperatures warming up again well into the 50s and later on into the 60s once again, over 10 degrees above average, as a stronger, longer lasting ridge builds into the region. Stay tuned for more information on the outlook for Thanksgiving.

Late this morning into early this afternoon, widespread light rain affected the area, and as temperatures aloft dropped below freezing and surface temperatures dropped into the 40s, there were a few reports of light snow showers mixing with the rain in the interior Northeast, towards western NJ, interior southern CT and parts of New England.

Although temperatures at the 850mb and 925mb are below freezing across most of the area, the precipitation is not heavy enough to result in snow, and as a result, light rain is falling across the area, potentially mixing with snowflakes towards interior Connecticut. In this type of an event, heavier precipitation is needed to bring the colder air aloft down to the surface to bring a better chance of snow; in southern NJ, where moderate rain is falling, Cape May and Atlantic City are seeing temperatures in the upper 30s, while in New York City, where light rain is falling, temperatures are in the mid 40s. If moderate precipitation was falling across the area right now, it would have been in the form of snow across a larger part of the area.

Looking at the latest radar posted above, the rain has ended west of NYC, and the western end of the rain is starting to move east in western Long Island/Connecticut. In LI/CT, light to moderate rain will continue to fall over the next 2-3 hours, occasionally mixing with snow showers towards interior Connecticut, before ending by at least 8 PM. Clearing skies will take place overnight with low temperatures dropping into the lower to mid 20s near NW NJ and Orange county in NY, mid 20s to lower 30s in the rest of NE NJ, Rockland/Westchester counties and southern CT, upper 20s to lower 30s in Long Island, and lower to mid 30s in NYC. Stay tuned for a brief update on the longer range forecast this evening, including the outlook for Thanksgiving.

Wednesday, November 16, 2011

Note: Today's update is a short one, with a discussion focusing on tomorrow's expected storm. Another brief update will be posted tomorrow; the next full update will be posted on Saturday. In addition, the winter outlook will be delayed until Wednesday, 11/23.

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Tomorrow's Outlook: Rain Expected; Snow Possible

Although the forecasting models usually nail down storms in the short range, in some cases there are weak storms that the models do not catch up to until the short range, and tomorrow is another one of these cases. The models have indicated for the last few days that a secondary wave of low pressure could form on Thursday, and I did mention on my update from Monday, when some models failed to show any secondary storm, that a wave of low pressure would develop but would do so on Wednesday night and stay offshore. It was not until yesterday that the models began showing more widespread precipitation affecting the area.

This is in the very short range, with less than 24 hours left until the event, but the models have been trending further west with the storm, with the SREF and GFS bringing light to moderate precipitation in the area. The NAM, although keeping most of the precipitation to the south and east of NYC, has trended further west and wetter as well, and if the latest trends are in fact correct, may end up even further west by its next run early tomorrow morning. The short range RUC model agrees with this trend as well, bringing precipitation as far west as eastern Pennsylvania. Exactly how far west the storm ends up is uncertain as this is a last minute change in the forecast, but it is likely that the majority of the area, if not the entire area see some precipitation out of this storm.

With the storm moving through the area at the same time that a strong trough moves in, the potential is there that not only rain falls out of this storm. With precipitation falling, colder air would be pulled closer to the surface, with temperatures below the 925mb layer ending up near to below freezing. Although not enough cold air is in place to support snow falling down to the sea level, meaning that NYC and its immediate surroundings would see light to moderate rain tomorrow, enough cold air is in place that should moderate precipitation fall tomorrow afternoon and evening as far west as northern NJ, snow would likely mix with the rain especially in the higher elevations of northern NJ, SE NY and Connecticut. The storm also means that high temperatures would end up colder than what most forecasts currently suggest; should the latest trend placing the precipitation over the area verify, temperatures would peak during the day in the lower to mid 40s from NYC and further west and in the mid to upper 40s in Long Island and southern Connecticut. The actual 24-hour highs would be at 12 AM as temperatures drop throughout the overnight hours as the cold front moves through.

Overall, light rain is expected to develop across the area again tomorrow morning, lasting through the evening hours, with occasionally moderate rain possible in NYC and Long Island. As colder air moves in, snow may mix with the rain in interior northern NJ and SE NY, although little to no accumulations are expected. The precipitation will end by tomorrow evening as skies clear and temperatures drop into the mid 20s to lower 30s across most of the area for lows. Stay tuned for a few short updates on this storm tomorrow afternoon.

Longer Range Forecast Overview:

- Cold temperatures continue on Friday with mostly sunny skies, peaking in the lower to mid 40s inland and the mid to upper 40s across the area. As a ridge rebuilds into the region again, mostly sunny skies will continue on Saturday with highs in the lower to mid 50s across the area.

- Sunday will bring partly cloudy skies with warmer temperatures, peaking in the upper 50s to lower 60s across the area, and a few mid 60s may be possible near and SW of NYC in the warmer case scenario. A cold front will move through overnight, bringing mostly cloudy skies and a few showers.

- Monday and Tuesday are expected to be mainly dry, with partly sunny skies and a transient trough producing near to slightly below average temps, with highs in the mid 40s to lower 50s across the area and lows in the upper 20s to upper 30s likely.

- There is more uncertainty afterwards, but some models suggest that a storm may be possible on Wednesday and Thursday of next week. The models are still having difficulties handling this time frame, however, so details may still change with this storm. The outlook for Thanksgiving will be discussed in more details on Saturday.

- Behind the potential Wednesday-Thursday storm, yet another ridge will build into the central and eastern US as the cold that has built up to that point in southern and central Canada is weakened by the strongly positive EPO, likely bringing drier conditions with warmer temperatures for the weekend.

9:55 PM: Since last night, there have been increasing indications that another storm will affect the area tomorrow during the day as well, instead of clearing skies. This storm, however, will fall around the same time that the cold air moves in, and last minute trends on the models are suggesting that the interior parts of the area may see snow during the day tomorrow. The 5-Day Forecast page was updated at 7 PM today reflecting this potential, and I will post a slightly more detailed discussion by 11 PM regarding this change in the forecast.

Monday, November 14, 2011

With the ridge in the eastern US still firmly in place, the area observed partly to mostly cloudy skies today with warm temperatures. The model guidance from yesterday, however, underestimated the warmth by as much as 5-10 degrees in parts of the region, and temperatures ended up warmer than expected, peaking in the lower 60s inland, mid to upper 60s in the immediate NYC area, and the mid 60s across most of Long Island and southern Connecticut. Places such as Teterboro and Newark in NE NJ reached 70 degrees, which is over 15 degrees above the average for this time of the year.

With a cold front near the area, tomorrow won't bring any big surprises with the temperatures as mainly cloudy skies are expected with isolated showers possible. A wave of low pressure will move through the area on Wednesday, bringing moderate rain across the area, making this the first significant precipitation event in over half a month to affect the area. Although colder temperatures will return behind, with below freezing lows across most of the area on Thursday night, the cold will fail to last much longer as yet another ridge builds in, bringing temperatures back into the 60s by next weekend.

Tomorrow's Outlook:

Tomorrow will bring mainly cloudy skies as a cold front responsible for producing a severe weather outbreak in the Ohio Valley today moves towards the area. This front will not produce any severe weather or thunderstorms in the area as the front will dry up with no instability over the region, instead bringing isolated showers as the precipitation will focus on a wave of rain developing in the Southeast along this front. With the front's proximity to the area, tomorrow will bring slightly cooler temperatures, peaking in the lower to mid 60s inland, mid 60s in the immediate NYC area, and the lower to mid 60s east of NYC. Places near or SW of NYC may reach the upper 60s.

Wednesday - Friday: Rain Moves Through, Then Colder

The wave of rain affecting the area on Wednesday will be the first significant precipitation event for the area in over half a month, since the late October snowstorm. This storm won't bring widespread heavy rain, although a steady light to moderate rain is expected throughout the day, ending by the evening hours as the front moves to the east of the area and a colder air mass moves in. High temperatures will be chilly due to the rain, peaking in the mid to upper 50s across the area, possibly in the lower 60s in parts of Long Island/S CT and near NYC.

Although a colder air mass will move in, cloud cover will continue through Wednesday night as another weak wave of low pressure develops but stays offshore this time, keeping the rain to the east of the area. With a trough over the region on Thursday, NW winds will bring colder temperatures while producing lake effect rain/snow near the Great Lakes region, resulting in mostly to partly sunny skies and high temperatures peaking in the mid to upper 40s inland and the upper 40s to lower 50s across the rest of the area.

The coldest temperatures are expected for Thursday night, when a high pressure moving into the region will bring mostly clear skies. Low temperatures will drop into the mid to upper 20s inland, upper 20s to lower 30s in the north/west suburbs of NYC and southern CT, upper 20s to mid 30s in Long Island, and the mid 30s in NYC. As the trough starts to exit the region on Friday, the high pressure in place will provide mostly sunny skies with chilly temperatures, peaking in the mid to upper 40s across most of the area with a few lower 50s possible near NE NJ/NYC.

Saturday - Tuesday: Warming Up, Then Cold Front Moves Through

Behind the trough, yet another ridge will build into the region for next weekend. With the high pressure sliding offshore, mostly sunny skies will continue on Saturday with high temperatures reaching the lower to mid 50s across the area. By Saturday night, however, a stronger low pressure will move through the Midwest and into Canada, bringing a snowstorm to places such as Minnesota. This will bring SW winds for Sunday with warmer temperatures, likely reaching the lower to mid 60s across most of the area again. There is some uncertainty with the exact timing of the cold front, but it appears that it should be close enough to the region to bring partly to mostly cloudy skies with a risk of showers focusing around the Sunday night time frame. With the storm staying well to the north of the area, however, any rain associated with the cold front should be light.

Due to the uncertainty with the cold front timing, the forecast for Monday is also somewhat uncertain. For now, I am expecting temperatures to slightly cool down into the mid to upper 50s with a risk of showers towards the morning hours, but the forecast is subject to change, and it is possible that the cold front may trend slightly slower, increasing Monday's temperatures while bringing more of a rain chance. Cooler temperatures are expected to return by Monday night/Tuesday as another transient trough moves into the Northeast, and while the forecast towards the middle of next week becomes more uncertain, several models have been hinting at a potential storm towards the mid week. This is still uncertain, however, and more information will be posted on the outlook for next week, including the forecast for Thanksgiving weekend, over the next few days.

Longer Range: For now, I have not changed my thoughts on the pattern going into early December. My next full discussion on the longer range will be with the final winter outlook, which will include a detailed discussion on the pattern going into December as well as when the pattern may change towards a colder and snowier one.

Sunday, November 13, 2011

With a low pressure near south central Canada along with a strong high pressure off the eastern US driving out the cold from the Northeast US, a strong ridge began building into the region today, bringing warmer temperatures along with partly to mostly cloudy skies, reaching the mid to upper 50s inland and the upper 50s to lower 60s across the rest of the area.

The ridge will continue to build into the region, but unlike the last ridge, when widespread well above average temperatures were observed up to the Ohio Valley, a stalled cold front will keep the area near the edge of the warmer temperatures as several waves of low pressure move up along the front, with the final and stronger wave bringing widespread moderate rain on Wednesday. Although colder temperatures will return on Thursday and Friday with parts of the area dropping below freezing for the overnight lows, the pattern will prevent this cold spell from becoming sustained, and there are strong indications pointing that an even stronger warm spell than the current one may set up by next weekend.

Tomorrow's Outlook:

With a cold front approaching the region, mostly cloudy skies are expected across the area tomorrow, and although a risk of scattered showers is in place, potentially bringing a brief period of moderate rain especially to the west of NYC, widespread rain is not expected to fall across the area throughout the day. Along with a SW wind and 850 mb temperatures remaining near 10 degrees celsius, temperatures tomorrow will be slightly warmer than those of today, peaking in the upper 50s to lower 60s inland and the lower to mid 60s across the rest of the area.

Tuesday - Wednesday: Slightly Cooler, Widespread Rain Returns

The outlook for Tuesday and Wednesday became increasingly uncertain over the last few days as the model guidance had issues with handling the cold front and the waves of low pressure, but today a stronger consensus has emerged, with the model guidance showing the front near the area on Tuesday. With the front over the area, temperatures will end up similar to those of today, peaking in the upper 50s inland, and the lower 60s across the rest of the area, along with mostly cloudy skies and scattered showers. If the front is slightly to the west of the current expectation or if there is more sunshine, temperatures may get close to 65 degrees in parts of the immediate NYC area, although this is starting to appear not as likely as it did yesterday.

The front will finally move through the area late on Wednesday as a wave of low pressure brings the first significant precipitation event to the area in over half a month, since the late October snowstorm. This feature was the most variable on the models over the last few days, with some showing the cold front to our east on Wednesday, others keeping the storm to the west of the area with more warmth, and some did not show the secondary wave at all. There is still some uncertainty with the location and timing of the wave on Wednesday, but it appears that widespread rain should fall across the area. If the scenario currently expected verifies, occasional light to moderate rain would fall across the area throughout the day and into the evening/early overnight hours, with high temperatures peaking in the lower to mid 50s inland and the mid 50s across the rest of the area, potentially in the upper 50s in parts of the immediate NYC area. Temperatures could end up slightly warmer than expected if the rain is weaker or further west, with highs reaching the mid 50s to lower 60s across the area in that scenario. The rain is expected to continue throughout the day before ending by the early overnight hours, with a total of 1/2 to 1 inch of rain possible across the area. Stay tuned for more information on Wednesday's storm.

Thursday - Early Next Week: Cold, Then Warming Up

During the time that the wave of rain will affect the area on Wednesday, a strong trough will drop into the north central US, with 850 mb temperatures dropping slightly below -10 degrees celsius. Under this pattern, occasional cold spells, sometimes strong, will affect the region, but due to the pattern in the Pacific consisting of a -PNA and a +EPO, these troughs are only transient and quickly move out, replaced by more ridging in the East Coast. This will be the case once again, as a cold ending to the week is expected followed by a warmer weekend.

The trough will move into the area on Thursday, bringing clearing skies, breezy winds, and high temperatures in the mid 40s inland and the upper 40s across the rest of the area, possibly near the lower 50s in parts of the immediate NYC area. With mostly clear skies, colder temperatures are expected on Thursday night, dropping into the mid 20s to lower 30s across most of the area with mid 30s expected in NYC. Mostly sunny skies and chilly temperatures are expected for Friday, with highs likely in the mid to upper 40s across the area, potentially getting near 50 degrees in parts of the immediate NYC area.

As we have seen several times this month, in this time frame, and again beyond this time frame, the trough will move out of the region by Friday night, with yet another ridge building by Saturday and Sunday. With a very negative PNA expected, a rising EPO and the NAO/AO trending towards positive, there are strong indications that a significant warm spell is expected between Sunday and Monday, potentially including Tuesday. Temperatures as a result will gradually warm up throughout the weekend, reaching the lower to mid 50s across the area on Saturday, and likely getting into the upper 50s to lower 60s across the area on Sunday. Partly sunny skies are expected during the weekend. The warmest temperatures are likely to take place on Monday; should the cold front stay to the west of the area as currently expected, widespread temperatures in the lower to mid 60s are expected, potentially getting into the upper 60s in parts of the immediate NYC area in the warmer case scenario where there is more sunshine and the ridge remains solidly in place over the region.

Longer Range: Pattern To Stick Around Through Early December

The teleconnections supportive of a mild pattern will peak early next week, with a strongly negative PNA, +EPO, +AO and +NAO, all of which strongly support warmth in the East Coast. After early next week and towards Thanksgiving weekend, however, the PNA will become less negative, and there are some indications that the NAO may trend back towards neutral or slightly negative. The positive EPO, however, will send more warmth while pushing out the strong cold air starting to build over western Canada. Although slightly more frequent cool spells may be possible towards the end of the month and into early December, the -PNA/+EPO pattern will remain in place, delaying any pattern change and likely keeping mainly above average temperatures through early December. This does not mean that December will fail to produce cold and snow, however, as it appears that the pattern change is simply delayed but not canceled. When the pattern changes is still uncertain, but at this time, it is unlikely that a mild pattern without snow persists through all of December. My final winter outlook, which will be posted next Sunday, will discuss the pattern outlook for December in more details.

Saturday, November 12, 2011

As the trough in place over the region yesterday moved out, today brought a breezy SW wind, with gusts peaking in the 20-30 mph range across most of the area. With the cold moving out, warmer temperatures returned, with high temperatures peaking in the mid 50s across most of the area and the mid to upper 50s in the immediate NYC area.

As we have already seen twice so far this month, another strong ridge will develop over the eastern US behind this trough, with temperatures once again getting to near 70 degrees early next week, near 15 degrees above the average for this time of the year. A cold front will move through the area between Tuesday night and Wednesday, bringing a stronger trough with near average temperatures by the second half of next week, although not surprisingly, this trough will quickly move out as well, which will be followed by above to well above average temperatures returning once again by next weekend, bringing no end to the warm pattern in sight.

Tomorrow's Outlook:

With the ridge building into the region, a SSW wind is expected for tomorrow, although the winds won't be as strong as today, with gusts locally up to 20-25 mph possible. The SSW winds, along with warmer temperatures aloft, will bring warmer temperatures into the area, reaching the upper 50s to lower 60s across most of the area. Temperatures will get close to 65 degrees in parts of the immediate NYC area.

Monday - Wednesday: Unseasonably Warm

With a trough in the western US, a strong ridge will remain in place on Monday, with the SSW wind persisting. 850 mb temperatures warming up to nearly 10 degrees celsius will result in even warmer temperatures, reaching the lower to mid 60s across the area with the warmest temperatures in the immediate NYC area. Partly to mostly cloudy skies are expected on Monday, and although an isolated shower may be possible, no widespread showers are expected on Monday and Monday night.

By Tuesday, a stronger cold front will move towards the region. With warmer temperatures spreading into the area from the southwest, widespread highs in the mid to upper 60s are expected across the area. Mostly cloudy skies are expected, but if there is more sunshine than currently expected, parts of NE NJ may reach the 70 degree mark, which is over 15 degrees above average for this time of the year. No rain is expected to fall during the day at this time, although a slight risk of showers is in place especially towards the afternoon and evening hours. As the front approaches the area, light to moderate rain is expected to fall on Tuesday night, and while still uncertain, some models extend the risk of rain through Wednesday. For now, I am keeping only a slight risk of rain in the forecast for Wednesday, although the forecast is still subject to change. If the models trend towards this scenario, I may change my forecast to slightly lower Tuesday's temperatures while slightly warming Wednesday's temperatures, reaching the lower to upper 60s, along with a higher rain risk. Stay tuned for more information on Tuesday and Wednesday's storm.

Behind this cold front, a trough will move into the region, bringing colder temperatures for Thursday and Friday. The exact intensity of the cold air mass is uncertain, but colder 850 mb temperatures are expected, likely dropping below -5 degrees celsius. This will result in high temperatures dropping into the mid 40s to lower 50s across the area, with low temperatures likely in the mid 20s to mid 30s, with the coldest temperatures inland and the warmest temperatures in NYC. Friday's temperatures will slightly warm up into the upper 40s to lower 50s across most of the area.

So far, we have a slightly negative NAO pattern, although the NAO is east based, which is not supportive of cold in the East US, but the pattern is dominated by a very strong negative PNA and a positive EPO, which is keeping a warm pattern locked over the eastern half of the US. As we have seen and will see through the rest of this month, there will be occasional cold spells in this pattern, but as long as the -PNA and the +EPO pattern persists, these troughs will remain transient, quickly moving out as more ridges build over the eastern US, resulting in a warmer than average pattern. With no change in the pattern, this upcoming weekend will bring another trough into the western US, and not surprisingly, another ridge will build into the eastern US, likely focusing on the Saturday to Tuesday time frame, 11/19 to 11/22. The intensity and the timing of the warmth is still uncertain considering the time range, but if the overall set up ends up close to the current thinking and what we have seen so far under this pattern, it is very possible that widespread highs in the mid to upper 60s return towards this time frame, potentially bringing yet another round of well above average temperatures.

There are a few signs showing improvement in the Pacific pattern towards slightly more cold in the East, including a moderating -PNA, trending towards neutral, although the EPO and AO remain positive with the NAO trending towards slightly positive as well. Considering the teleconnections and the pattern we are in, a turn to a colder pattern is unlikely before early December, and if we do turn to a more sustained cold/potentially snow pattern, it would likely wait until early to mid December at the earliest, if not slightly afterwards. Stay tuned for more information on the long range pattern.

Friday, November 11, 2011

Behind last night's cold front, the ridge over the region was replaced by a strong trough, with partly sunny skies and windy conditions observed today. With the trough in place, colder high temperatures were observed, only peaking in the mid to upper 40s inland, upper 40s to lower 50s in the immediate NYC area, and the lower 50s across most of Long Island and southern CT. Wind gusts ended up in the 30-40 mph range across most of the area as expected.

This trough is only making a brief appearance in the area, however, as a stronger ridge will build back into the region tomorrow and on Monday, bringing well above average temperatures across the region once again. A cold front will approach the area on Tuesday, bringing showers to the area especially between the afternoon and the overnight hours, and while colder temperatures will return behind the front along with drier conditions, the pattern will remain unfavorable for any sustained cold to develop in the northern US.

Tomorrow's Outlook:

With the trough moving out, 850 mb temperatures will warm up, passing the zero degree celsius mark. With a breezy SW wind expected along with mostly sunny skies, surface temperatures will warm up as well, reaching the mid 50s across most of the area, with a few upper 50s possible in parts of the immediate NYC area. Wind gusts are expected to reach the 20-30 mph range across most of the area.

Next Week: Warming Up, Some Rain, Then Colder

The current pattern with a strong -PNA, going off the charts, as well as an east based -NAO, is unfavorable for cold setting up over the northern US, and this appears to be the case once again, as another trough dropping into the western US will result in a ridge building into the region once again for Sunday and Monday. This will bring mostly sunny skies on Sunday with highs in the upper 50s to lower 60s across the area, and partly to mostly cloudy skies across the area on Monday with highs in the lower to mid 60s across most of the area. Parts of the immediate NYC area may reach the upper 60s if there is enough sunshine, which would end up nearly 15 degrees above the average high temperature for this time of the year.

A cold front will approach the region on Monday. Yesterday's models were faster with the front, with the GFS bringing it through on Monday, although today's models trended slower, and are now in agreement with showing the front moving through on Tuesday night. As a result, temperatures will remain in the lower to potentially mid 60s across most of the area on Tuesday with showers expected between the afternoon and overnight hours. Light to moderate rain is likely to fall across most of the area, although no significant rainfall amounts are expected.

Behind this front, cooler temperatures will gradually return. High temperatures are likely to cool down into the lower to mid 50s across most of the area between Wednesday and Friday, and one of these days may end up with temperatures in the mid 40s to lower 50s although the exact timing is uncertain, depending on a potential weak low pressure in the Northeast that some models show on Thursday. This potential low pressure won't bring more than a few rain showers to the area, although it would bring slightly warmer temperatures on Thursday with colder temperatures on Wednesday and Friday. This cold spell will not be sustained as well, and another ridge could build again by next weekend with warmer temperatures. Stay tuned for more information on the outlook for next week.

Longer Range: Will The Cold Set Up?

Over the last several days, there have been indications that a more sustained cold pattern could build towards the end of the month. The PNA, although currently very negative, is shown to trend closer to neutral, allowing for a weaker ridge in the eastern US, with a trend towards a slightly negative NAO in the longer range and the MJO trending towards phases 1-2, as well as building strong cold air in western Canada. There are more indications, however, that the pattern may not change as early, with the Pacific pattern potentially remaining unfavorable for strong cold dropping into the US through the rest of November, and there are already some similarities appearing compared to the winter of 2001-2002, which brought very little snow to the NYC area. I am not expecting this winter to end up nearly as snowless as that winter did, and a cold and snowy December is still a reasonable possibility, although the possibility that a colder pattern may fail to materialize for December cannot be ruled out. Stay tuned for more information on the longer range with updates over the next few days. The outlook for December will be discussed in more details with my final winter outlook, which will be posted on Sunday, 11/20.

Thursday, November 10, 2011

Note: I was unable to update the 5-Day Forecast and the Long Range Outlooks pages today. An updated 5-Day Forecast will be posted during Friday morning, and the discussion for the late November outlook will be posted with tomorrow evening's update.

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As a cold front moved through the area today, pushing out the ridge that has been stuck over the region for the last few days, mild temperatures were observed prior to the frontal passage. The forecast from yesterday was too cold for the western half of the area, as unexpected sunny skies during the afternoon allowed temperatures to surge into the upper 60s from NYC and further west, while expected cloud cover and rain in Long Island and southern Connecticut resulted in high temperatures peaking in the lower to mid 60s, verifying yesterday's forecast for that part of the area. Rainfall amounts ended up between 1/4 and 1/2 inch in the eastern parts of Long Island and SE Connecticut, and light to moderate rain currently moving into the immediate NYC area will bring up to 1/4 inch tonight.

Behind this cold front, a strong trough will briefly drop into the region, bringing high temperatures into the 40s and 50s again across the area along with windy conditions. Although this cold spell will not last long under the current pattern, with another ridge building by Sunday and Monday, gradual changes in the pattern will result in weaker warm spells across the area by the second half of the month.

Tomorrow's Outlook:

With the strong trough over the area along with a tight pressure gradient and 850 mb temperatures near -5 degrees celsius, cold and windy conditions are expected across the area tomorrow. A strong NW/WNW wind is expected gusting up to 30-40 mph across most of the area, although it is not out of the question that a few parts of the area exceed 40 mph wind gusts. High temperatures will be much colder than those of today, peaking in the mid to upper 40s inland, upper 40s to lower 50s in the immediate NYC area with a few mid 50s possible south of NYC, and in the lower to mid 50s in Long Island and southern CT.

Weekend Outlook: Warming Up

Tropical Storm Sean, currently to the west of Bermuda, will be absorbed by this trough, and a strong non-tropical low pressure currently developing east of New England will quickly intensify while moving to the north. This intensifying storm will pull the trough along with it at the same time that another trough drops into the western US, resulting in yet another strong ridge building into the eastern US. This ridge will not be as warm as the current ridge, although it will bring above average temperatures once again to the area. With a high pressure moving into the region at the same time, mostly sunny skies are expected this weekend, along with high temperatures peaking in the mid 50s across most of the area on Saturday, slightly higher in parts of the immediate NYC area, and in the upper 50s to lower 60s on Sunday.

Next Week's Outlook: Rain Returns, Then Increasing Uncertainty

The latest model guidance has trended towards a weaker ridge in the western Atlantic, failing to hold strong as modeled yesterday and instead remaining mainly south. Most of the latest models then push the cold front through the area on Monday and Tuesday, bringing rain followed by colder temperatures. The models appear to have issues with handling the pattern next week, as each model shows a different scenario; the GFS quickly brings in a strong trough by the second half of next week, the CMC keeps ridging in place, while the ECMWF has several storms moving through the central US, keeping the cold stuck to the northwest of the region while bringing more rain chances.

There is a high probability for rain to fall around the Monday-Tuesday time frame, although the intensity of the rain and whether it affects only parts of the area or the entire area is still uncertain. At this time, I am expecting ridging to remain in place through at least Tuesday, with light to possibly moderate rain possible between Monday afternoon through Tuesday. The potential may be there for another low pressure to affect the region around Thursday, although this potential is still uncertain and depends on Tuesday's cold front and what comes behind it. Colder air will likely return by Wednesday, although it appears at this time that the better chance for stronger cold may be towards the end of the week. Stay tuned for more information on next week's outlook as details become clearer.

Wednesday, November 9, 2011

With the strong ridge persisting over the East Coast, today brought well above average temperatures to the area once again, with high temperatures ending up in the mid to upper 60s from NYC and further west and the lower to mid 60s in Long Island and southern Connecticut. Today was the last day of the mainly sunny and warm conditions for now, however, as a strong trough will move into the region tomorrow, bringing mainly cloudy skies and scattered showers, followed by much colder and windy conditions for Friday and Saturday.

The cold spell will only be brief, however, as the current pattern does not support sustained cold spells, and another large ridge will build into the eastern US for Sunday and the first half of next week. The trend of a lack of significant rain events in the area started in late October will continue again, however, as no major rain event appears to be on the way, although some rain is likely for the middle of next week as a cold front moves through, bringing another brief cold spell.

Tomorrow's Outlook:

With the cold front moving towards the area tomorrow and Tropical Storm Sean approaching from the SE, stormy conditions will affect the region. Sean itself will not be the main storm, as parts of Sean will become a stronger extra-tropical storm that will move east of New England on Thursday night. This will keep scattered showers in the area between the afternoon and early overnight hours in the area, although less than 1/4 inch of rain is expected from NYC and further west, with the potential for over 1/2 inch in eastern Long Island and SE CT. Due to the increased cloud cover and the cold front moving through, high temperatures will be colder, peaking in the upper 50s to lower 60s inland and the lower to mid 60s across the rest of the area. With the front moving through, variable wind direction is expected tomorrow, although a mostly WNW wind will develop by the evening.

Friday - Sunday: Cold/Windy Start, Sunny/Mild Ending

With the extratropical storm moving into Canada, a strong trough will move into the region, bringing 850 mb temperatures to near -6 degrees celsius. Along with mostly to partly cloudy skies and a a gusty west/WNW wind, gusting up to 30-40 mph in parts of the area, much colder high temperatures are expected for Friday, peaking in the mid to upper 40s inland, upper 40s to mid 50s in the immediate NYC area, and the lower to mid 50s in Long Island and southern Connecticut.

The current pattern we are in does not favor sustained cold spells over the region. With a strong -PNA pattern keeping a trough over the western US, sustained cold is not favored in the eastern US, although a weak east based -NAO is allowing for some brief troughs to drop into the region. With yet another trough dropping into the western US, the trough in place will quickly lift out of the region, with a strong ridge building by Sunday. Temperatures will slightly warm up throughout the weekend with mostly sunny skies, peaking in the mid 50s in the immediate NYC area and the lower to mid 50s elsewhere on Saturday, and the lower 60s in the immediate NYC area and upper 50s to lower 60s elsewhere on Sunday.

Next Week's Outlook: Warmer Start, Colder Ending

As another low pressure stays north of the Great Lakes region during Sunday, a weak cold front will approach the region on Monday but will fail to move through. As a result, mostly cloudy skies are expected with SSW winds and the risk of isolated showers across the area. In the scenario that it does not rain, warmer temperatures are expected, reaching the lower to mid 60s across the area, and parts of NE NJ and further southwest may exceed the 65 degree mark if there is more sunshine than currently expected. More widespread showers than currently modeled may keep the temperatures slightly lower.

By Tuesday, a stronger low pressure is expected to develop near the Ohio Valley/Great Lakes region, moving northeast. This low pressure will keep the mild temperatures in place for Tuesday across the area with partly to mostly cloudy skies still expected, and at this time, there is a stronger model consensus for the cold front to move through during Wednesday. As a result, rain is expected to affect the area on Tuesday night into Wednesday, although no widespread moderate-heavy rain is expected at this time. There is still some slight uncertainty with the exact timing, and it is possible that the front may move through a little earlier or later than currently expected.

(This section was revised on the morning of 11/10). There is more uncertainty for the second half of next week due to the time range, although it is likely that another trough tries to move into the region behind this storm. There is uncertainty with the timing, as some models keep the front stuck nearby with another storm for the late week. The GFS, which is the fastest and driest model, only has weak ridging in the western Atlantic, which may be too weak given that the majority of the other models show a stronger ridge, which would make it more difficult for the trough to move in immediately. One possible scenario is where the front then moves through with mostly dry conditions in the second half of the week followed by a high pressure building in by Friday/Saturday, although as some of these models are suggesting, another low pressure may be possible in the second half of the week. Tonight's update will discuss this in more details, along with a discussion for the pattern towards end of November into December.